EP0520943A1 - Positive displacement pump - Google Patents

Abstract

In a positive displacement pump for incompressible fluids, which has two spiral-shaped discharge chambers (6) which lead from an inlet (2) outside the spiral to an outlet (3) inside the spiral, one spiral-shaped displacement body (5) each, which is arranged on a disk (4) and which projects into the discharge chamber (6), with a looping angle of 360 DEG is supported so as to perform a circular, torsion-free movement. The pressure in the outlet is kept constant in that the spring-supported (13) disk (4) with the displacement bodies (5) lifts from its sealing position as soon as the back pressure exceeds a predefined value. <IMAGE>

Description

Field of the Invention

The invention relates to a positive displacement pump for incompressible media, having at least one delivery space delimited by spiral peripheral walls extending perpendicularly from a side wall of a fixed housing, which leads from an inlet lying outside the spiral to an outlet lying inside the spiral, and with one in the Conveying space protruding, spiral-shaped displacement body, which encompasses a wrap angle of 360 ° and which is mounted in relation to the delivery space to perform a circular, torsion-free movement and the center of which is eccentrically offset from the center of the peripheral walls in such a way that the displacement body is always both external and also almost touches the inner peripheral wall of the delivery chamber on at least one progressive sealing line,

State of the art

Such a machine, the principle of which is known, for example, from US 2,841,089, is suitable for conveying liquids. During the operation of such a machine, along the conveying space between the displacer and the two peripheral walls of the conveying space Includes crescent-shaped workspaces that move from the inlet through the delivery chamber to the outlet. Such spiral machines with a wrap angle of 360 ° convey only because they work without internal compression. With an increasing number of circular movements per unit of time, the funding volume also increases. The pressure in the outlet is independent of the suction pressure in the inlet and is specified by the consumer. With increasing pressure in the outlet, the power requirement naturally also increases.

If such a displacement pump is to be used, for example, to convey the lubricant in internal combustion engines and the pump is driven directly by the internal combustion engine in the simplest way, the following problems must be taken into account: The speed range and thus the number of circular movements of the displacement body change by a factor of 10 under the condition that the engine is properly supplied with lubricant between idle speed and full load speed. This means that the displacement pump must be designed for the minimum consumption of 10 liters per minute, for example. According to the above, the pump would deliver the 10 times the amount that is of course not required at full load. Another problem arises with regard to the lubricant temperatures which, for example in the case of lubricating oil, can easily vary between -20 ° C and 120 ° C. This temperature difference of 140 ° C leads to strongly varying viscosity of the oil, which in turn affects the efficiency of the positive displacement pump. The consequence of this is that the pump has to be designed for the highest occurring temperatures. A third problem arises from the consumer: Manufacturing tolerances and wear in the internal combustion engine lead to different resistance and thus to different pressures in the outlet of the displacement pump. Accordingly, this must be designed from the outset for the greatest possible wear on the engine.

The displacement pump is therefore designed and dimensioned according to the most extreme conditions. On the occasion of operation in non-extreme conditions, which is the rule, the adaptation must be carried out with a blow-off valve as a countermeasure. Apart from the machine, which is usually oversized, this leads to the following disadvantages: The unnecessarily expended energy is then not only used unused due to the necessary blowing off, but is also directly misused by heating the recirculating oil. In addition, blowing off the oil via a pressure relief valve leads to foam formation, which significantly affects the lubricating properties.

From FR 2.195.270 it is known to install spring-assisted relief valves in the non-circulating delivery rooms in spiral machines. In this known machine, the conveyor spiral encloses an angle of 720 °. Due to the given internal compression, it is an actual scroll compressor for compressible media. However, the spring-assisted relief valves are not a measure to limit the delivery pressure or the delivery rate, but the intention is to prevent the backflow from an inside delivery chamber into an adjacent, further outside delivery chamber. If the spiral of this machine had only a wrap angle of 360 °, as is essential to convey incompressible means, the relief valves would not be required.

Presentation of the invention

The invention aims to prevent all the disadvantages mentioned in connection with displacement pumps for liquids. It is therefore based on the task of designing a positive displacement pump of the type mentioned at the outset as a pressure-constant, self-regulating pump.

According to the invention, this is achieved in that the orbiting disk with the displacement body is axially displaceably connected to a drive shaft which penetrates the housing and is mounted therein, and in that spring means which act directly on the rear of the disk and which are supported in the interior of the housing, the disk with the displacement body presses and seals against the side wall, and that the spring means are designed so that when a predetermined working fluid pressure in the outlet is reached, the disk with the displacement body disengages from its sealing position to such an extent that the working fluid pressure remains constant, regardless of the number of circular movements over time and regardless of Funding volume.

It is already known from US Pat. No. 2,841,089 mentioned at the beginning to press the disk with the displacement body against the cooperating walls of the delivery chamber via spring means in order to achieve the desired sealing effect in the delivery room. However, these spring means are primarily intended to press a co-absorbing sealing arrangement against the housing so as to seal the storage space against the delivery space. It is not possible to disengage the disc there due to permanent pressing using structural means such as bearing rings and shaft collars.

Brief description of the drawing

• Fig.1 einen Querschnitt durch eine erste Verdrängungspumpe nach Linie I-I in Fig.2;
• Fig.2 einen Längschnitt durch die Verdrängungspumpe nach Linie II-II in Fig.1
• Fig.3 einen Querschnitt durch eine Ausführungsvariante der Verdrängungspumpe nach Linie III-III in Fig.4;
• Fig.4 einen Längschnitt durch durch eine Ausführungsvariante der Verdrängungspumpe nach Linie IV-IV in Fig.3

In the drawing, two exemplary embodiments of the subject matter of the invention are shown schematically.
It shows:

• 1 shows a cross section through a first displacement pump according to line II in Figure 2;
• 2 shows a longitudinal section through the displacement pump according to line II-II in Fig.1
• 3 shows a cross section through a variant of the displacement pump according to line III-III in Figure 4;
• 4 shows a longitudinal section through a variant of the displacement pump according to line IV-IV in FIG

In the drawing, all parts which are not essential for understanding the invention, such as the drive, the fixing of the housing parts to one another and to the consumer, etc., have been omitted. Parts of the two design variants with the same designation are provided with the same reference symbols in the figures. The direction of flow of the working medium is indicated by arrows.

Way of carrying out the invention

The pump shown in FIGS. 1 and 2 is equipped with two nested conveying spaces 6 and displacement bodies 5 lying therein. It goes without saying that an entire system of spirals arranged in this way can be provided in the same plane. All of these spirals can convey more advantageously from their own inlet 2 into a common outlet 3.

To explain the functioning of the pump, which could be used as a lubricating oil pump for internal combustion engines, reference is made to the prior art mentioned at the beginning. Only the pump structure and process sequence necessary for understanding the invention are briefly described below.

The disk-shaped rotor is designated as a whole by 1. The spiral-shaped displacement bodies 5 are arranged on one side of the disk 4. Their spirals extend over a wrap angle of 360 °. They engage in a delivery chamber 6 of the fixed housing 7. They are dimensioned in their axial extent so that with their narrow end faces, both at standstill and during operation, they represent the groove bottom of the delivery rooms, i.e. almost touch the disc side 20. The conveying space 6 is worked into the housing 7 in the manner of a spiral slot. It runs from an inlet 2 arranged on the outer circumference of the spiral in the housing to an outlet 3 arranged inside the housing. It has essentially parallel circumferential walls 8, 9 which are arranged at a constant distance from one another and which, like the displacement body, have a spiral of 360 here ° include. The displacement body 5 is guided between these circumferential walls 8, 9. Its curvature is such that it almost touches the inner and outer peripheral walls at the same time. For this purpose, the center 10 of the displacement body 5 is offset eccentrically with respect to the center 11 of the delivery chamber 6. The spiral shape of the delivery chamber and displacement body is made up of two semicircular arches. Of course, other spiral shapes are also possible.

During operation of the pump, the eccentric drive of the disk-shaped rotor 1 carrying the displacement bodies 5 results in a circular movement of each of the points of the displacement bodies, this circular movement being limited by the peripheral walls of the delivery spaces. As a result of the multiple, alternating approach of the displacement bodies to the inner and outer circumferential walls, alternating crescent-shaped working spaces enclosing the working medium result on the inner and outer sides of the displacement bodies. These working spaces become through on the occasion of the circular movement of the displacement bodies the delivery rooms are pushed towards the common outlet.

In the case shown in FIG. 1, two end positions of the displacement bodies 5 are shown. The outside diameter of the disc 4, which cannot be seen in this section, is shown in dashed lines. The spiral 5a lies both at its entry-side end and at its exit-side end with its inside against the inner peripheral wall 8 of the delivery chamber 6. On the one hand, it thus encloses the crescent-shaped work space 12 with its inside. On the other hand, the spiral is open on its outside against both inlet 2 and outlet 3, i.e. at the same time, it sucks in and discharges there, as indicated by the corresponding arrows. The spiral 5b, however, is in the second end position. It encloses the working space 12 with its outside and is opened with its inside against the inlet 2 and the outlet 3. These offset spiral positions result in two outputs per circular movement, which results in low-pulsation conveyance.

For the sake of clarity, the system of the displacer 5 is rotated by 90 ° in relation to the representation in FIG. 1 in the longitudinal section in FIG. This in order to be able to better show the eccentricity e between the drive and the rotor as well as between the displacement body and the delivery spaces in the section plane. The external feed of the two inlets 2, which can take place in any manner, is not shown.

The two housing halves 7 and 7 'are connected to one another via screw connections 29 only indicated in FIG. The drive shaft 14, which penetrates the housing 7 ', is arranged coaxially to the delivery spaces 6. The centers of the delivery rooms in turn run in the middle of the circular housing part 7. The shaft bearing 18 is located within a with the housing half 7 ' Integrated bushing 24. A blind bore 26, offset by eccentricity e, is provided within a shaft collar, via which the connection to the axially displaceable rotor 1 takes place. This connection takes place in the form of a pin 15 protruding from the disk 4. This pin engages in the blind hole 26 via the pin bearing 17. The journal bearing 17 and the shaft bearing 18 are lubricated by means of the working fluid which is fed by the spirals. For this purpose, the disk 4 and the pin 15 are provided with a longitudinal bore 16 which communicates with the outlet 3. The lubricant under pressure is supplied to the respective bearing points via transverse bores 19 in the journal and 21 in the shaft collar. The lubricant emerging from the bearing points is passed through a transverse bore 22 in the shaft collar and through a bore 23 in the housing bushing 24 into the interior of the housing half 7 'connected to the inlets 2.

The spring means 13 are also located in this interior, which ensure that the pressure in the outlet 3 does not exceed a predetermined level. In the present case, it is a helical spring that surrounds the bush 24. At one end, this spring is supported on the inner wall of the housing half 7 '. With its other end, it acts directly on the rear side of the disc 4, which is not provided with displacement bodies. Since this disc orbits during operation, the adjacent spring requires a guide. The disc is therefore provided with an annular extension 25 on the corresponding diameter. On its free end face there is a groove in which the tongue lies.

The spring means are now designed with a certain strength and according to a certain characteristic. In such a way that when a predetermined pressure in the outlet 3 is exceeded, the pressure on the inner circular surface of the disk 4 and on the adjacent one against the outlet open sickle surfaces of the conveying spaces, sufficient force is sufficient to lift the disc with the displacement body slightly out of its normal sealing position. Here, the pin 15 moves a little deeper into the blind bore 26. The axial movement of the rotor 1 is minimal. Due to the resulting leaks on the end faces of the displacement bodies and the end walls of the delivery spaces, pressurized working fluid flows from the inside working spaces into the outside working spaces and vice versa, depending on the position of the displacement bodies. This reduces the pressure in the outlet until the spring force is sufficient to press the rotor against the housing in the sealing position.

This means that - regardless of the drive speed and the back pressure - the pump only delivers the volume that is required by the consumer. In one example, would the supply line to the consumer be closed for any reason, i.e. the delivery rate would be zero, so that due to the pressure build-up in outlet 3, the rotor would immediately lift out of the sealing position to such an extent that all the fluid conveyed by a work space flows over the end faces of the spirals into the radially opposite work space. The pump therefore runs empty, it does not deliver and the power requirement drops. This means that this self-regulating pump differs significantly from the conventional bypass methods, whereby it is characterized by the fact that the lubricant cannot foam due to the internal pump recirculation.

The displacement pump according to FIGS. 3 and 4 differs in terms of the delivery parts in that three displacement bodies 5, which are distributed uniformly over the circumference, are arranged on the disk 4. The corresponding associated three promotion rooms 6 are from a common inlet 2 fed. So although the spirals convey from the outside in, the supply of the spirals with work equipment takes place in the most direct way from the center of the housing. From the three outlets 3, the working fluid reaches a common annular chamber 27, from where it is fed to a consumer (not shown).

• Die Spirale 5a liegt sowohl an ihrem eintrittsseitigen Ende als auch an ihren austrittsseitigen Ende mit ihrer Aussenseite an der äusseren Umfangswand 8 des Förderraumes 6 an. Einerseits schliesst sie somit mit ihrer Aussenseite den sichelförmigen Arbeitsraum 12 ein. Andererseits ist die Spirale an ihrer Innenseite sowohl gegen den Einlass 2 als auch gegen den Auslass 3 geöffnet, d.h. gleichzeitig saugt sie dort an und stösst dort aus, wie durch die entsprechenden Pfeile angedeutet.
• Die Spirale 5b hingegen steht in einer zweiten, um 120° verschobenen Stellung. Sie liegt mit ihrer Aussenseite und mit ihren Innenseite nur in je einem Punkt an den entsprechenden Umfangswänden des Förderraumes an. Sie schliesst somit keinen geschlossenen Arbeitsraum 12 ein. Die Aussenseite des Verdrängungskörper ist gegen den Einlass 2 geöffnet; der entsprechende Arbeitsraum ist schon weitgehend gefüllt. Die Innenseite des Verdrängungskörper ist gegen den Auslass 3 geöffnet; der Austossvorgang geschieht in vollem Umfang.
• Die Spirale 5c schliesslich steht in der dritten, gegenüber der ersten Spirale um 240° verschobenen Stellung. Sie liegt wie die Spirale 5b ebenfalls mit ihrer Aussenseite und mit ihren Innenseite nur in je einem Punkt an den entsprechenden Umfangswänden des Förderraumes an und schliesst somit keinen geschlossenen Arbeitsraum ein. Die Innenseite ihres Verdrängungskörpers ist noch gerade gegen den Einlass 2 geöffnet und ist dabei, den Ansaugvorgang zu beenden. Die Aussenseite des Verdrängungskörper ist gegen den Auslass 3 geöffnet und ist dabei, den Austossvorgang zu beenden.

In the case shown in Figure 3, three positions of the displacement body 5 are shown. Here, too, the outside diameter of the disc 4, which cannot be seen in this section, is shown in dashed lines.

• The spiral 5a bears with its outer side against the outer peripheral wall 8 of the delivery chamber 6 both at its inlet end and at its outlet end. On the one hand, it thus encloses the crescent-shaped work space 12 with its outside. On the other hand, the inside of the spiral is open both against the inlet 2 and against the outlet 3, ie at the same time it sucks in and discharges there, as indicated by the corresponding arrows.
• The spiral 5b, however, is in a second position shifted by 120 °. It lies with its outside and with its inside only at one point on the corresponding circumferential walls of the delivery room. It therefore does not include a closed work space 12. The outside of the displacement body is opened towards the inlet 2; the corresponding work space is already largely filled. The inside of the displacement body is opened against the outlet 3; the ejection process takes place in full.
• Finally, the spiral 5c is in the third position, which is shifted by 240 ° with respect to the first spiral. Like the spiral 5b, it also lies with its outside and with its inside only at one point on each corresponding peripheral walls of the delivery room and thus does not include a closed work area. The inside of her displacement body is just open against the inlet 2 and is about to end the suction process. The outside of the displacement body is opened against the outlet 3 and is about to end the ejection process.

These offset spiral positions result in two times three ejections per circular movement, which results in an even lower pulsation delivery.

The drive and storage of the rotating and rotating parts is the same as for the version according to Fig. 2. On the other hand, pressureless working fluid from the interior of the housing is used to lubricate the bearings. It is fed to the respective bearing points via the bores 23 in the bushing 24 and 21 in the shaft collar 14.

The spring means 13 used here are a number of helical springs arranged uniformly over the circumference. At one end, these springs are supported by ball joints 28 in corresponding pans on the inner wall of the housing half 7 '. With their other end, they also act directly on the rear side of the disc 4, which is not provided with displacement bodies, via ball joints, which is also equipped with ball sockets on the corresponding diameter for this purpose.

REFERENCE SIGN LIST

1

runner

2nd

inlet

3rd

Outlet

4th

disc

5.5a, 5b, 5c

Displacement body

6

Funding area

7.7 ′

casing

8th,

inner peripheral wall of FIG. 6

9

outer peripheral wall of 6

10th

Center of the sinker spirals

11

Center of the delivery space spirals

12

working space

13

Spring means

14

drive shaft

15

Cones

16

Hole in 15

17th

Pin bearing

18th

Shaft bearing

19th

Cross hole in 15

20th

Side wall

21

Cross hole in 14

22

Cross hole in 14

23

Hole in 24

24th

Rifle in 7 ′

25th

Approach to 4

26

Blind hole in 14

27th

Ring chamber

28

Ball joint

29

Screw connection

e

eccentricity

Claims (5)

Displacement pump for incompressible media, with at least one delivery chamber (6) delimited by spiral peripheral walls (8,9) extending vertically from a side wall (20) of a fixed housing (7,7 '), which is connected by an inlet ( 2) and an outlet (3) lying inside the spiral, and with a spiral displacement body (5), which is arranged on a disc (4) and projects into the conveying space (6), which comprises a wrap angle of 360 ° and which in With respect to the conveying space for carrying out a circular movement, the center (10) of which is offset eccentrically from the center (11) of the peripheral walls (8, 9) such that the displacement body (5) always has both the outer and the inner peripheral wall (9 or 8) of the delivery chamber (6) almost touches at least one advancing sealing line,
characterized,
that the orbiting disc (4) with the displacement body (5) is axially displaceably connected to a drive shaft (14) penetrating the housing (7 ') and mounted therein and that spring means (13) acting directly on the rear side of the disc (4), which are supported in the interior of the housing (7 '), the disc (4) with the displacement body (5) presses and seals against the side wall (20), and that the spring means (13) are designed so that when a predetermined working fluid pressure is reached in the outlet (3) the disk (4) with the displacement body (5) disengages from its sealing position so far that the working fluid pressure remains constant, regardless of the number of circular movements over time and regardless of the delivery volume. Displacement pump according to Claim 1, characterized in that the connection of the disk (4) to the drive shaft (14) takes place via a pin (15) which is mounted eccentrically in a blind bore (26) in the shaft (14). Displacement pump according to Claim 2, characterized in that in the region of the outlet (3) the disk (4) and the pin (15) of the drive shaft are provided with a bore (16) through which the medium of the pin bearing (17 ) and the shaft bearing (18) can be fed. Displacement pump according to Claim 1, characterized in that two displacement bodies (5) rotated 180 ° relative to one another are arranged nested one inside the other on the disk (4), and in that the corresponding nested corresponding two delivery spaces (6) open into a common outlet (3). Displacement pump according to Claim 1, characterized in that at least three displacement bodies (5) distributed uniformly over the circumference are arranged on the disk (4), and in that the correspondingly arranged, associated at least three delivery spaces (6) open into a common inlet (3).

Images